Conventionally, a teleconference system used for sharing video and audio among a plurality of bases connected via a communication network to hold a conference has been provided. However, in the conventional system, there is a problem in that degradation of sound and image quality often occurs, due to deterioration in the communication state of the communication network. The degradation of sound and image quality causes huge stress on the parts participants of the conference, and if the degradation is too severe, it is not possible to continue the conference.
In relation to this point, Japanese Patent Application Laid-open No. 2010-093505 (Patent Literature 1) discloses a communication system that increases the ratio of bandwidth for audio communication as compared with bandwidth for image communication in response to deterioration in the communication state of the communication network, to prevent degradation of sound quality so as to enable the participants of the conference to at least mutually understand what the other has said in any case.
However, the degradation of sound and image quality occurs not only by the transmission delay of the communication network, but also occurs substantially due to the internal processing delay (processing time from when data is received to when an output signal is generated) at the data receiving side. Thus, an expected effect, may not be obtained by just focusing on the communication state of the communication network as in Patent Literature 1.